scsi-block: fix direction of BYTCHK test for VERIFY commands

The direction is wrong; scsi_block_is_passthrough returns
false for commands that *can* use sglists.

Reported-by: Zhang Qian <zhangqian@sangfor.com.cn>
Fixes: 8fdc7839e4
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/scsi/scsi-disk.c

@@ -2701,7 +2701,7 @@ static bool scsi_block_is_passthrough(SCSIDiskState *s, uint8_t *buf)
          * for the number of logical blocks specified in the length
          * field).  For other modes, do not use scatter/gather operation.
          */
-        if ((buf[1] & 6) != 2) {
+        if ((buf[1] & 6) == 2) {
             return false;
         }
         break;